Battery system housing with integrated cooling pipe

ABSTRACT

A battery pack for an electric vehicle is disclosed. The battery pack includes an upper tray, a first busbar attached to the upper tray, a lower tray, and a second busbar attached to the lower tray. The battery pack also includes a plurality of battery cells arranged in the upper and lower trays, and a cooling duct contacting the lower and upper trays.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. Nonprovisionalapplication Ser. No. 15/468,542, filed Mar. 24, 2017, which claims thebenefit of and priority to U.S. Provisional Application No. 62/384,298,filed Sep. 7, 2016, the disclosures of which are hereby incorporated byreference in their entirety for all purposes.

BACKGROUND

An electric vehicle uses one or more electric motors powered byelectrical energy stored in a rechargeable battery system. Lithium-basedbatteries are often chosen for their high power and energy density. Inorder to ensure that an electric vehicle operates efficiently andsafely, the temperature of the battery system must be maintained withina defined range of optimal temperatures. The coolant system of electricvehicle can be physically extended to the battery system to removeexcess heat, thereby increasing the service life of the battery systemand increasing the distance that can be traveled on a single charge.

As the popularity of electric vehicles increases, efficiency in themanufacturing process will become more important. Processes and devicesthat decrease the cost of manufacturing battery systems whilesimultaneously increasing their reliability and safety will be key tomeeting customer demands. Specifically, there is a need for processesand devices that ensure reliable electrical connections betweenindividual battery cells, that efficiently cool the battery system, andthat aid in the manufacturing process of assembling the thousands ofindividual battery cells into modular systems that can be installed andreplaced when necessary.

BRIEF SUMMARY OF THE INVENTION

Aspects of the present disclosure relate to battery systems and methodsof making and/or manufacturing the battery systems, and some aspects ofthe present disclosure relate to busbars and specifically to busbarsincluding an integral busbar cooling duct.

One inventive aspect is a battery pack for an electric vehicle. Thebattery pack includes an upper tray, a first busbar attached to theupper tray, a lower tray, and a second busbar attached to the lowertray. The battery pack also includes a plurality of battery cellsarranged in the upper and lower trays, and a cooling duct mechanicallyconnecting the lower tray to the upper tray.

In some embodiments, the cooling duct is configured to transfer avertical force between the upper and lower trays. In some embodiments,while the cooling duct transfers the vertical force between the upperand lower trays, the battery cells transfer substantially no forcebetween the upper and lower trays.

In some embodiments, the cooling duct is integrated with the lower tray.

In some embodiments, the cooling duct is integrated with the upper tray.

In some embodiments, the cooling duct is separate from the upper andlower trays.

The battery pack of claim 1, where the cooling duct includes fluidchannels configured to conduct a cooling fluid.

Another inventive aspect is a method of manufacturing a battery pack foran electric vehicle. The method includes attaching a busbar to an uppertray, attaching first sides of a plurality of battery cells to the uppertray, attaching second sides of the battery cells to the upper tray, andconnecting a cooling duct to at least one of the lower tray and theupper tray.

In some embodiments, the cooling duct is configured to transfer avertical force between the upper and lower trays. In some embodiments,while the cooling duct transfers the vertical force between the upperand lower trays, the battery cells transfer substantially no forcebetween the upper and lower trays.

In some embodiments, the cooling duct is integrated with the lower tray,and connecting the cooling duct to at least one of the lower tray andthe upper tray includes connecting the cooling duct to the upper tray.

In some embodiments, the cooling duct is integrated with the upper tray,and connecting the cooling duct to at least one of the lower tray andthe upper tray includes connecting the cooling duct to the lower tray.

In some embodiments, the cooling duct is separate from the upper andlower trays, and connecting the cooling duct to at least one of thelower tray and the upper tray includes connecting the cooling duct tothe upper tray and to the lower tray.

In some embodiments, the cooling duct includes fluid channels configuredto conduct a cooling fluid.

Another inventive aspect is an electric vehicle powered by a batterypack. The battery pack includes an upper tray, a first busbar attachedto the upper tray, a lower tray, and a second busbar attached to thelower tray. The battery pack also includes a plurality of battery cellsarranged in the upper and lower trays, and a cooling duct mechanicallyconnecting the lower tray to the upper tray.

In some embodiments, the cooling duct is configured to transfer avertical force between the upper and lower trays. In some embodiments,while the cooling duct transfers the vertical force between the upperand lower trays, the battery cells transfer substantially no forcebetween the upper and lower trays.

In some embodiments, the cooling duct is integrated with the lower tray.

In some embodiments, the cooling duct is integrated with the upper tray.

In some embodiments, the cooling duct is separate from the upper andlower trays.

In some embodiments, the cooling duct includes fluid channels configuredto conduct a cooling fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the remaining portions of thespecification and the drawings, wherein like reference numerals are usedthroughout the several drawings to refer to similar components. In someinstances, a sub-label is associated with a reference numeral to denoteone of multiple similar components. When reference is made to areference numeral without specification to an existing sub-label, it isintended to refer to all such multiple similar components.

FIG. 1 illustrates a simplified diagram of an electric vehicle with arechargeable battery system, according to some embodiments.

FIG. 2 illustrates a lithium-based battery that may be used in electricvehicles, according to some embodiments.

FIGS. 3A and 3B are cross-sectional views of a battery pack.

FIGS. 4A-4G is a series of views illustrating a process of manufacturinga battery pack.

FIG. 5 is a flowchart illustrating one embodiment of a process formanufacturing a rechargeable battery pack.

FIG. 6 is a flowchart illustrating an embodiment of a process formanufacturing a vehicle having a rechargeable battery system.

DETAILED DESCRIPTION OF THE INVENTION

Described herein are embodiments for providing a busbar comprising anintegral busbar cooling duct. The integral busbar cooling duct simplifythe design of a battery pack by eliminating the need for separatecomponents for cooling the busbar and/or the battery cells in thebattery pack. In some embodiments, the busbar cooling duct can define avolume through which a cooling fluid such as, for example, a refrigerantcan flow. The cooling fluid can be liquid, gaseous, or a combination ofliquid and gaseous.

In some embodiments, the busbar cooling duct can be fluidly connect to acooling system that can include, for example, a heat exchanger. In someembodiments, the cooling system and/or the heat exchanger can be a partof the battery pack and/or can be separate from the battery pack.

The busbar cooling duct can comprise a variety of shapes and sizes. Insome embodiments, the busbar cooling duct can comprise an elongatechannel that can have, a polygonal cross-section, a circularcross-section, a semi-circular cross-section, and/or any other desiredshape of cross-section. In some embodiments, the busbar cooling duct canbe straight, curved, angled, zig-zag, serpentine, circular, or the like.

FIG. 1 illustrates a simplified diagram 100 of an electric vehicle 102with a rechargeable battery system 104, according to some embodiments.The rechargeable battery system 104 may be comprised of one or morebattery modules or packs 106. A battery pack may be comprised of aplurality of individual battery cells that are electrically connected toprovide a particular voltage/current to the electric vehicle 102. Insome embodiments, the battery cells forming the battery pack can bearranged in one or several rows of battery cells. Depending on theembodiment, the electric vehicle 102 may include hybrid vehicles thatoperate using both fuel combustion and stored electric power, as well asfully electric vehicles that operate entirely from stored electricpower.

The rechargeable battery system 104 represents a major component of theelectric vehicle 102 in terms of size, weight, and cost. A great deal ofeffort goes into the design and shape of the rechargeable battery system104 in order to minimize the amount of space used in the electricvehicle 102 while ensuring the safety of its passengers. In someelectric vehicles, the rechargeable battery system 104 is located underthe floor of the passenger compartment as depicted in FIG. 1. In otherelectric vehicles, the rechargeable battery system 104 can be located inthe trunk or in the hood areas of the electric vehicle.

While a smaller number of larger battery cells could be moreenergy-efficient, the size and cost of of these larger batteries areprohibitive. Furthermore, larger batteries require more contiguousblocks of space in the electric vehicle 102. This prevents largerbatteries from being stored in locations such as the floor of thepassenger compartment as depicted in FIG. 1. Therefore, some embodimentsuse a large number of smaller battery cells that are coupled together togenerate electrical characteristics that are equivalent to single largercells. The smaller cells may be, for example, the size of traditionalAA/AAA batteries, and may be grouped together to form a plurality ofbattery packs 106. Each battery pack may include a large number ofindividual battery cells. In one embodiment, 700 individual lithium-ionbatteries are joined together to form each of a number of single batterypacks 106 a, 106 b, 106 c, and 106 d, and the rechargeable batterysystem 104 may include the four battery packs 106 a, 106 b, 106 c, and106 d. In some embodiments, the rechargeable battery system 104 includeeight battery packs, ten battery packs, sixteen battery packs, oranother number of battery packs, connected in parallel or series untilthe electrical requirements of the electric vehicle 102 are satisfied.The individual battery cells included in each battery pack 106 may totalin the thousands for a single electric vehicle 102.

In some embodiments, the rechargeable battery system 104, andspecifically one or several of the battery packs 106 can be connected toa heat exchanger 108 that can be a part of a cooling system 110. In someembodiments, the cooling system 110 can be part of the rechargeablebattery system 104 and in some embodiments, the cooling system 110 canbe separate from the rechargeable battery system 104. The cooling system110 can include connecting lines 112 that can fluidly connect the heatexchanger 108 to one or several of the battery packs 106. The connectinglines 112 can include an inlet line 114 and an outlet line 116. Theinlet line 114 can transport a cooling fluid, such as a refrigerant tothe rechargeable battery system 104 and/or to one or several batterypacks 106. In some embodiments, the cooling fluid can be contained inthe cooling system 110, in the rechargeable battery system 104, and/orin one or several battery packs 106.

FIG. 2 illustrates a diagram 200 of a lithium-based battery 202 that maybe used in electric vehicles, according to some embodiments. As usedherein, the terms “battery”, “cell”, and “battery cell” may be usedinterchangeably to refer to any type of individual battery element usedin a battery system. The batteries described herein typically includelithium-based batteries, but may also include various chemistries andconfigurations including iron phosphate, metal oxide, lithium-ionpolymer, nickel metal hydride, nickel cadmium, nickel-based batteries(hydrogen, zinc, cadmium, etc.), and any other battery type compatiblewith an electric vehicle. For example, some embodiments may use the 6831NCR 18650 battery cell from Panasonic®, or some variation on the 18650form-factor of 6.5 cm×1.8 cm and approximately 45 g. The battery 202 mayhave at least two terminals. In some embodiments, a positive terminal204 may be located at the top of the battery 202, and a negativeterminal 206 may be located on the opposite bottom side of the battery202.

In some embodiments, some or all of the battery cells forming a batterypack 106 can be oriented in the same direction. In other words, thepositive terminal of each of the individual battery cells may face in anupward (or downward) direction relative to the battery pack, and each ofthe negative terminals faces in a downward direction. In otherembodiments, this need not be the case. Alternating rows of individualbattery cells may be oriented in opposite direction such that thepositive terminal of a first row is oriented in the up direction and thepositive terminal of a second row is oriented in the downward direction.The orientation pattern for individual battery cells may vary withoutlimitation. For example, every other battery cell in a row be orientedin opposite directions. In some embodiments, one half of the batterypack may have battery cells oriented in one direction, while the otherhalf of the battery pack has cells oriented in the opposite direction.In any of these cases, connections may need to be established betweenbatteries oriented in opposite directions or between batteries orientedin the same direction.

In order to make electrical connections between battery cells, a busbarmay be used. As used herein, the term “busbar” refers to any metallicconductor that is connected to a plurality of individual battery cellterminals in order to transmit power from the individual battery cellsto the electrical system of the electric vehicle. In some embodiments,the busbar may comprise a flat metallic sheet that is positioned on thetop or the bottom of the battery pack. In some embodiments, the metallicsheet may cover an entire top or bottom of the battery pack, while inother embodiments, the busbar may comprise a strip that is longer thanit is wide to interface with a single row of battery cells.

FIGS. 3A and 3B are illustrations of battery pack 300, which includesbattery cells 310, lower tray 330, upper tray 340, busbars 350, andbusbar 355. Battery pack 300 also includes one or more busbars not shownconnected to the underside of lower tray 330. In alternative embodimentsother numbers of battery cells are used. For example, in someembodiments, a battery pack includes 700 or another number of batterycells.

As shown, battery cells 310 are arranged so as to engage indentations inlower tray 330 and upper tray 340. Because of the indentations, lowertray 330 and upper tray 340 provide mechanical support which resistslateral or shearing forces. In some embodiments, lower tray 330 andupper tray 340 are nonconductive. For example lower tray 330 and uppertray 340 may be formed with an injection molded plastic.

In addition, battery cells 310 are arranged so as to be supported bycooling duct 320, which, in this embodiment, is integrated with lowertray 330. In alternative embodiments, cooling duct 320 is separate fromlower tray 330, and engages lower tray 330 for example in grooves,similar to the engagement between cooling duct 320 and upper tray 340,discussed below. In some embodiments, cooling duct 320 is integratedwith upper tray 340.

Cooling duct 320 also provides mechanical support resisting lateral orshearing forces. In addition, cooling duct 320 provides mechanicalsupport to the battery cells during manufacturing, as discussed furtherbelow. Cooling duct 320 also includes fluid channels 325, through whicha cooling fluid may be circulated so as to provide a path through whichheat may be removed from the battery cells 310.

Cooling duct 320 also provides mechanical support protecting batterycells 310 from forces of vertical impact. For example, battery pack 300may be configured such that cooling duct 320 transfers a vertical forcebetween upper and lower trays 340 and 330 with substantially no verticalforce being transferred by the battery cells 310.

Busbars 350 and 355 are mechanically connected with upper tray 340. Forexample, the busbars 350 and 355 may be glued or welded to upper tray340. Other attachment mechanisms may be used. Busbars 350 and 355 areconductive and provide electrical connections to the battery cells 310.Busbars 350 and 355 also provide mechanical support which resistsflexing forces experienced by upper tray 340.

In this embodiment, busbar 350 also includes a plurality of contacts352. The plurality of contacts 352 are configured to electricallyconnect one or several portions and/or layers of the busbar 350 with oneor several battery cells 310, and specifically to the terminals of oneor several battery cells 310. In some embodiments, one or several of theplurality of contacts 352 can be electrically connected with one orseveral conductive layers of the busbar 350 and/or with one or severalconductive materials forming the busbar 350.

In this embodiment, busbar 355 also includes a plurality of contacts357. The plurality of contacts 357 are configured to electricallyconnect one or several portions and/or layers of the busbar 355 with oneor several battery cells 310, and specifically to the terminals of oneor several battery cells 310. In some embodiments, one or several of theplurality of contacts 352 can be electrically connected with one orseveral conductive layers of the busbar 355 and/or with one or severalconductive materials forming the busbar 355.

The battery cells 310 may be oriented such that busbar 350 provides anelectrical connection with battery cell terminals of a first polarityand busbar 355 provides an electrical connection with battery cellterminals of a second polarity. For example, busbar 350 may provide anelectrical connection with positive battery cell terminals, and busbar355 may provide an electrical connection with negative batteryterminals. Alternatively, busbar 350 may provide electrical connectionwith negative battery terminals, and busbar 355 may provide electricalconnection with positive battery terminals.

FIGS. 4A-4H is a series of views illustrating a process of manufacturinga battery pack, such as battery pack 300 of FIGS. 3A and 3B.

FIG. 4A is a view of an upper tray 440. Upper tray 440 may, for example,be formed with an injection molded plastic, or another nonconductivematerial.

FIG. 4B is a view of upper tray 440 having busbars 450 and 455 attachedthereto. Busbars 450 and 455 may comprise a conductive metal, and may befixed to upper tray 440 with an adhesive material, a glue, an epoxy, orwith another mechanism, such as a weld. In some embodiments, busbars 450and 455 are attached to upper tray 440 through a heating process, whichmelts or partially melts the material of upper tray 440 such that oncefrozen, the material of upper tray 440 is fixed to busbars 450 and 455.

FIG. 4C is a view of a lower tray 430. Lower tray 430 may, for example,be formed with an injection molded plastic, or another nonconductivematerial. In the illustrated embodiment, lower tray 430 includes coolingduct 420 having multiple fluid channels 425.

FIG. 4D is a view of lower tray 430 having busbar 458 attached thereto.The busbar 458 may comprise a conductive metal, and may be fixed tolower tray 430 with an adhesive material, a glue, an epoxy, or withanother mechanism, such as a weld. In some embodiments, busbar 458 isattached to lower tray 430 through a heating process, which melts orpartially melts the material of lower tray 430 such that once frozen,the material of lower tray 430 is fixed to busbar 458.

FIG. 4E is a view of lower tray 430 having busbar 458 attached thereto.Busbar 458 is on the opposite side of lower tray 430 shown. Contacts 459of busbar 458 are visible through the holes 432 of lower tray 430.

As illustrated, lower tray 430 includes indentations 434 having shapeswhich correspond with an outline of a plurality of battery cells. Inthis embodiment, indentations 434 are configured to receive sevenbattery cells.

FIG. 4F is a view of lower tray 430, battery cells 410, and cooling duct420. Battery cells 410 are placed in lower tray 430 so that theterminals of battery cells 410 near lower tray 430 electrically connectwith contacts 459 of busbar 458, and so that the battery cells 410engage and are held in place by the indentations 434 of lower tray 430.In addition, cooling duct 420 provides additional mechanical support tothe battery cells 410 during manufacturing, such that the battery cells410 are less likely to be removed from lower tray 430 by, for example,lateral or other forces. In some embodiments, the battery cells 410 arefixed to lower tray 430 with, for example, a glue, an epoxy, or anotherfixing mechanism.

FIG. 4G is a view of the manufactured battery pack 400. As shown, uppertray 440 having busbars 450 and 455 attached thereto, has been attachedto battery cells 410 such that the battery cells 410 engage and are heldin place by the indentations of upper tray 440, and the terminals ofbattery cells 410 near upper tray 440 engage and form electricalconnections with the contacts 452 of busbar 450 and engage and formelectrical connections with the contacts 457 of busbar 455. In addition,cooling duct 420 engages grooves 445 in upper tray 440. In someembodiments, the battery cells 410 are fixed to upper tray 440 with, forexample, a glue or another fixing mechanism. In some embodiments,cooling duct 420 is fixed to upper tray 440 with, for example, a glue oranother fixing mechanism.

In some embodiments, battery pack 300 may be configured such thatcooling duct 420 transfers a vertical force between upper and lowertrays 440 and 430 with substantially no vertical force being transferredby the battery cells 410.

FIG. 5 is a flowchart illustrating one embodiment of a process 500 formanufacturing a rechargeable battery pack, such as those discussedherein. The method can include, for example, a process for manufacturingone or several battery packs 106 of rechargeable battery pack system104, discussed above with reference to FIG. 1.

The process begins at block 510, and may include attaching one or morebusbars to a lower tray. The lower tray may be, for example, formed of anonconductive plastic material, and may have indentations configured toreceive battery cells. The one or more busbars may be attached to thelower tray on a side opposite the indentations. The one or more busbarsmay be attached to the lower tray using a glue or another fixingmechanism.

At 510, the process may additionally or alternatively include attachingone or more busbars to an upper tray. The upper tray may be, forexample, formed of a nonconductive plastic material, and may haveindentations configured to receive battery cells. The one or morebusbars may be attached to the upper tray on a side opposite theindentations. The one or more busbars may be attached to the upper trayusing a glue or another fixing mechanism.

The process 500 may also include attaching battery cells to the lowertray as shown in block 520. In some embodiments, the battery cells arefixed to the lower tray with, for example, a glue or another fixingmechanism. The battery cells are attached to the lower tray such thatthe battery cells engage and are held in place by the indentations ofthe lower tray. In addition, the battery cells are attached to the lowertray such that the terminals of the battery cells near the lower trayform an electrical connection with the contacts of the busbars attachedto the lower tray.

The process 500 may also include attaching battery cells to the uppertray as shown in block 530. In some embodiments, the battery cells arefixed to the upper tray with, for example, a glue or another fixingmechanism. The battery cells are attached to the upper tray such thatthe battery cells engage and are held in place by the indentations ofthe upper tray. In addition, the battery cells are attached to the uppertray such that the terminals of the battery cells near the upper trayform an electrical connection with the contacts of the busbars attachedto the upper tray.

In alternative embodiments, the battery cells are fixed to the busbars,for example, with a glue, or another attachment mechanism, such as aweld. In such embodiments, the battery cells may additionally beattached to the upper tray and/or lower tray by a glue or anotherattachment mechanism. In some embodiments, the battery cells are heldagainst the upper tray and/or lower tray by the attachment mechanismattaching the battery cells to the upper tray and/or lower tray, and arenot otherwise attached to the upper tray and/or lower tray.

In alternative embodiments, the battery cells are not fixed to one orboth of the upper and lower trays. In such embodiments, the upper traymay be connected to the lower tray by a glue or another attachmentmechanism. In some embodiments, the battery cells are held against theupper tray and/or lower tray by the attachment mechanism attaching theupper tray to the lower tray, and are not otherwise attached to theupper tray and/or lower tray.

The process 500 may additionally include electrically connecting therechargeable battery system with a motor configured to provide power tothe vehicle.

It should be appreciated that the specific steps illustrated in '5provide particular methods of providing a rechargeable battery systemand/or a battery pack for an electric vehicle according to variousembodiments of the present invention. Other sequences of steps may alsobe performed according to alternative embodiments. For example,alternative embodiments of the present invention may perform the stepsoutlined above in a different order. Moreover, the individual stepsillustrated in FIG. 5 may include multiple sub-steps that may beperformed in various sequences as appropriate to the individual step.Furthermore, additional steps may be added or removed depending on theparticular applications. One of ordinary skill in the art wouldrecognize many variations, modifications, and alternatives.

FIG. 6 is a flowchart illustrating one embodiment of a process 600 formanufacturing a vehicle having a rechargeable battery system, such asthose discussed herein.

The process begins at block 610, and may include attaching arechargeable battery system to the vehicle, where the rechargeablebattery system includes an upper tray, a lower tray, a plurality ofbattery cells between the upper and lower trays, and a cooling ducthaving fluid channels between the upper and lower trays or integratedwith one of the upper and lower trays.

At 620, the process additionally includes attaching a cooling system tothe vehicle. The cooling system may, for example, have connecting linesconfigured to connect a heat exchanger to the rechargeable batterysystem. The connecting lines can include an inlet line and an outletline. The inlet line may be configured to transport a cooling fluid,such as a refrigerant to the rechargeable battery system. The outletline may be configured to transport the cooling fluid from therechargeable battery system to the cooling system.

The process 600 may also include, at 630, fluidly connecting the coolingduct, and specifically the fluid channels of the cooling duct to thecooling system. In some embodiments, connecting the cooling duct to thecooling system can include connecting fluid channels of the cooling ductto a heat exchanger of the cooling system. In some embodiments,connecting the cooling duct to the cooling system can include connectingthe cooling duct, and specifically the fluid channels of the coolingduct to the cooling system via connecting lines and specifically via aninlet line and/or via an outlet line.

The process 600 may also include filling the cooling system and thefluid channels of the cooling duct with a cooling fluid, which coolingfluid can be a refrigerant. In some embodiments, the filling of thecooling system and the fluid channels with a cooling fluid can alsoinclude filling a heat exchanger with the cooling fluid. In someembodiments, the cooling system can be configured to circulate thecooling fluid through the fluid channels of the cooling duct to maintaina desired temperature of the battery cells of the rechargeable batterysystem.

The process may additionally include electrically connecting therechargeable battery system with a motor configured to provide power tothe vehicle.

It should be appreciated that the specific steps illustrated in FIG. 6provide particular methods of providing a rechargeable battery systemand/or a battery pack for an electric vehicle according to variousembodiments of the present invention. Other sequences of steps may alsobe performed according to alternative embodiments. For example,alternative embodiments of the present invention may perform the stepsoutlined above in a different order. Moreover, the individual stepsillustrated in FIG. 6 may include multiple sub-steps that may beperformed in various sequences as appropriate to the individual step.Furthermore, additional steps may be added or removed depending on theparticular applications. One of ordinary skill in the art wouldrecognize many variations, modifications, and alternatives.

In the foregoing description, for the purposes of explanation, numerousspecific details were set forth in order to provide a thoroughunderstanding of various embodiments of the present invention. It willbe apparent, however, to one skilled in the art that embodiments of thepresent invention may be practiced without some of these specificdetails. In other instances, well-known structures and devices are shownin block diagram form.

The foregoing description provides exemplary embodiments only, and isnot intended to limit the scope, applicability, or configuration of thedisclosure. Rather, the foregoing description of the exemplaryembodiments will provide those skilled in the art with an enablingdescription for implementing an exemplary embodiment. It should beunderstood that various changes may be made in the function andarrangement of elements without departing from the spirit and scope ofthe invention as set forth in the appended claims.

Specific details are given in the foregoing description to provide athorough understanding of the embodiments. However, it will beunderstood by one of ordinary skill in the art that the embodiments maybe practiced without these specific details. For example, circuits,systems, networks, processes, and other components may have been shownas components in block diagram form in order not to obscure theembodiments in unnecessary detail. In other instances, well-knowncircuits, processes, algorithms, structures, and techniques may havebeen shown without unnecessary detail in order to avoid obscuring theembodiments.

Also, it is noted that individual embodiments may have been described asa process which is depicted as a flowchart, a flow diagram, a data flowdiagram, a structure diagram, or a block diagram. Although a flowchartmay have described the operations as a sequential process, many of theoperations can be performed in parallel or concurrently. In addition,the order of the operations may be re-arranged. A process is terminatedwhen its operations are completed, but could have additional steps notincluded in a figure. A process may correspond to a method, a function,a procedure, a subroutine, a subprogram, etc. When a process correspondsto a function, its termination can correspond to a return of thefunction to the calling function or the main function.

In the foregoing specification, aspects of the invention are describedwith reference to specific embodiments thereof, but those skilled in theart will recognize that the invention is not limited thereto. Variousfeatures and aspects of the above-described invention may be usedindividually or jointly. Further, embodiments can be utilized in anynumber of environments and applications beyond those described hereinwithout departing from the broader spirit and scope of thespecification. The specification and drawings are, accordingly, to beregarded as illustrative rather than restrictive.

What is claimed is:
 1. A battery pack for an electric vehicle, thebattery pack comprising: an upper tray, comprising a plurality of uppertopological features; a first busbar attached to the upper tray; a lowertray, comprising a plurality of lower topological features; a secondbusbar attached to the lower tray; a plurality of battery cells eachcomprising first and second opposing ends, wherein the first ends arearranged in and contact the upper topological features of the uppertray, and wherein the second ends are arranged in and contact the lowertopological features of the lower tray; and a cooling duct comprising amechanically supportive structure defining a fluid channel, wherein themechanically supportive structure extends between the lower tray and theupper tray substantially perpendicular to each of the lower tray and theupper tray, and wherein the mechanically supportive structure contactsand mechanically supports both the lower tray and the upper tray.
 2. Thebattery pack of claim 1, wherein the cooling duct is configured totransfer a force between the upper and lower trays.
 3. The battery packof claim 2, wherein while the cooling duct transfers the force betweenthe upper and lower trays, the battery cells transfer substantially noforce between the upper and lower trays.
 4. The battery pack of claim 1,wherein the cooling duct is integrated with the lower tray.
 5. Thebattery pack of claim 1, wherein the cooling duct is integrated with theupper tray.
 6. The battery pack of claim 1, wherein the cooling duct isnot integrated with either of the upper and lower trays.
 7. The batterypack of claim 1, wherein the fluid channel is configured to conduct acooling fluid.
 8. A method of manufacturing a battery pack for anelectric vehicle, the method comprising: attaching a first busbar to anupper tray, the upper tray comprising a plurality of upper topologicalfeatures; attaching first sides of a plurality of battery cells to theupper topological features of the upper tray; attaching a second busbarto a lower tray, the lower tray comprising a plurality of lowertopological features; attaching second sides of the battery cells to thelower topological features of the lower tray; and positioning a coolingduct between the lower tray and the upper tray, the cooling ductcomprising a mechanically supportive structure defining a fluid channel,wherein the mechanically supportive structure extends between the lowertray and the upper tray substantially perpendicular to each of the lowertray and the upper tray, and wherein the mechanically supportivestructure contacts and mechanically supports both the lower tray and theupper tray.
 9. The method of claim 8, wherein the cooling duct isconfigured to transfer a force between the upper and lower trays. 10.The method of claim 9, wherein while the cooling duct transfers theforce between the upper and lower trays, the battery cells transfersubstantially no force between the upper and lower trays.
 11. The methodof claim 8, wherein the cooling duct is integrated with the lower tray,and positioning the cooling duct comprises connecting the cooling ductto the upper tray.
 12. The method of claim 8, wherein the cooling ductis integrated with the upper tray, and positioning the cooling ductcomprises connecting the cooling duct to the lower tray.
 13. The methodof claim 8, wherein the cooling duct is separate from the upper andlower trays, and positioning the cooling duct comprises connecting thecooling duct to the upper tray and to the lower tray.
 14. The method ofclaim 8, wherein the fluid channel is configured to conduct a coolingfluid.
 15. An electric vehicle powered by a battery pack, the batterypack comprising: an upper tray, comprising a plurality of uppertopological features; a first busbar attached to the upper tray; a lowertray, comprising a plurality of lower topological features; a secondbusbar attached to the lower tray; a plurality of battery cells eachcomprising first and second opposing ends, wherein the first ends arearranged in and contact the upper topological features of the uppertray, and wherein the second ends are arranged in and contact the lowertopological features of the lower tray; and a cooling duct comprising amechanically supportive structure defining a fluid channel, wherein themechanically supportive structure extends between the lower tray and theupper tray substantially perpendicular to each of the lower tray and theupper tray, and wherein the mechanically supportive structure contactsand mechanically supports both the lower tray and the upper tray. 16.The electric vehicle of claim 15, wherein the cooling duct is configuredto transfer a force between the upper and lower trays.
 17. The electricvehicle of claim 16, wherein while the cooling duct transfers the forcebetween the upper and lower trays, the battery cells transfersubstantially no force between the upper and lower trays.
 18. Theelectric vehicle of claim 15, wherein the cooling duct is integratedwith the lower tray.
 19. The electric vehicle of claim 15, wherein thecooling duct is integrated with the upper tray.
 20. The electric vehicleof claim 15, wherein the cooling duct is separate from the upper andlower trays.
 21. The electric vehicle of claim 15, wherein the fluidchannel is configured to conduct a cooling fluid.